1. Field of the Invention
This invention relates to devices to indicate ballistic trajectories. Certain embodiments are particularly adapted for use to improve accuracy of bullet placement in long-range rifle shooting.
2. State of the Art
Accurate long-range shooting generally requires careful vertical alignment of a rifle barrel and sight system. A baseline trajectory typically assumes a projectile path is contained in a vertical plane. Conventionally, a sight element, such as a scope reticle, is placed into agreement with a vertical plumb line, and it remains up to the shooter to maintain that orientation when making a shot. Departure of the rifle and sight element from vertical agreement with the plumb line may be characterized as cant, which throws a projectile to either one side, or the other, as target range changes. The amount of undesired side travel of a projectile increases directly with increase in both range distance and cant angle.
Various arrangements have been developed to provide a shooter feedback that the rifle sight system is in a proper plumb orientation. It is known to provide a level-indicating element on a transversely-protruding lever element that can be removably anchored to a scope-mounting base. Such an arrangement undesirably positions the level-indicator in free space where the lever element is subject to damage from bumping into foreign objects. Bumping the protruding lever can knock the level-indicator out of its desired plumb orientation.
It is also known to include a level-indicator on a scope ring cap. However, great care must be taken when installing such a device, because the cap can be tightened down in an un-even fashion, and the gap between the top and bottom scope ring will allow the cap to be pulled out of plumb when tightening the cap-mounting screws.
It is also known to mount a level-indicator directly to a rifle scope. Unfortunately, this requires another level placed on the bolt rails of the rifle to get the gun level, then plumbing the cross hair in the scope to a vertical plumb line to get the whole setup plumb and level. The known prior art suffers by requiring a shooter to lift his/her head up from a conventional horizontal shooting position (raise his/her cheek from the rifle stock) to check the level to verify a proper shooting orientation of the system, just before pulling the trigger.
It would be an advance to provide a feedback system for proper rifle orientation that is simple to set up, robust to avoid accidental departure from a desired plumb orientation, and visible by a shooter from a cheek-down shooting position.